Japan (Scicasts) — Astronauts go through many physiological changes during their time in spaceflight, including lower muscle mass and slower muscle development. Similar symptoms can occur in the muscles of people on Earth's surface, too. In fact, it could affect everyone to some extent later in life.

"Age-related skeletal muscle disorders, such as sarcopenia, are becoming a greater concern in society," said Hiroshima University (HU) Professor and Space Bio-Laboratories Director Louis Yuge. "It is especially a big concern in Japan, where the number of ageing people is increasing."

In a study published in Microgravity, a medical research group at HU led by Yuge shed light on these similarities. They found that the process that affects gene expression of differentiating muscle cells in space also affects cells in the presence of gravity.

The genetic and molecular basis of impaired muscle development has been unclear. Yuge thinks there is a pressing need to understand it and come up with better treatment outcomes.

He and his team investigated how simulated microgravity - that is, gravity in space-like conditions - affects muscle cell differentiation and gene expression.

They observed what happened to rat muscle cells over time. Some cells were treated with a drug that stops DNA methylation from happening, while other cells were not. DNA methylation is a process that controls gene expression and muscle cell differentiation.

Next, they grew the cells either in normal gravity or inside of Gravite, a machine that simulates gravity at levels that astronauts experience in spaceflight. Cells in microgravity exhibited less cell differentiation after all. However, cells growing without the drug formed muscle fibres at a slower rate and showed less gene expression.

One gene, Myod1, was of particular interest. Its expression levels were significantly lower in microgravity conditions and when growing with the drug that stopped DNA methylation.

Within gravity, as well as without it, the group concluded that DNA methylation appears to be a key player in regulating muscle cell differentiation. "These findings highlight genes affected by DNA methylation, like Myod1, as potential targets for treating patients with skeletal muscle atrophy," Yuge said.

The team's results can be utilized in space experiments, where muscle atrophy of astronauts uses myotubes because it is easy to understand morphologically. Additionally, the findings of this epigenetics can be used in many differentiated cells, stem cells, or cancer. The Micro-G Center of the Kennedy Space Center of NASA, where Yuge is an advisory committee member, and NASA have already conducted experiments to cultivate stem cells on the International Space Station, where this paper can also provide insight. Yuge and his team are expected to start a massive space experiment at NASA/Center for Advancement of Science in Space (CASIS).

Houston, TX (Scicasts) — It all began with one young patient; a 7-year old boy who was born without a thymus, an important organ of the immune system, and without functional immune cells.

The boy also presented with cardiac and skeletal defects, dysmorphic craniofacial features and some signs of autistic behaviours.

"His physicians thought he had many features commonly seen in children with 22q11.2 chromosomal deletion syndrome," said corresponding author of this work Dr. Shinya Yamamoto, assistant professor of molecular and human genetics at Baylor College of Medicine and investigator at the Jan and Dan Duncan Neurological Research Institute at Texas Children's Hospital.

Interestingly, his sister and mother also exhibited similar defects but in a milder form. Surprisingly, none of them carried the 22q11.2 chromosomal deletion associated with this syndrome or had alterations in the TBX1 gene, which is located within this deletion.

"This spurred Duke University investigators Dr. Vandana Shashi and Dr. Loren Pena and genetic counselor Kelly Schoch, who are a part of the Undiagnosed Disease Network, to perform whole-genome sequencing analyses on this family," Yamamoto said.

These tests revealed the presence of a rare missense variant - p.R20Q - in the TBX2 gene in all three affected family members. In order to identify additional patients with rare variants in this gene, the team used GeneMatcher, a website developed by the Centers for Mendelian Genomics to connect physicians and researchers who share an interest in the same gene.

GeneMatcher led to the identification of a fourth patient seen by physicians at Cook Children's Hospital in Fort Worth, Texas. This patient shared many of the same clinical features present in the initial patient, but carried a different missense variant - p.R305H - in the TBX2 gene. TBX2 belongs to the T-box family of genes of evolutionarily conserved transcription factors that play crucial roles in the embryonic development of the heart, limbs, digits and brain regions. Alterations in 12 out of the 17 members of this gene family have been identified as causes of diverse multi-organ developmental syndromes in the past.

Further analyses conducted by postdoctoral fellows Dr. Ning Liu and Dr. Xi Luo at Baylor College of Medicine showed that the patients with the TBX2 genetic variants had decreased levels of TBX2 proteins. Having less protein led to reductions in the proteins' ability to carry out their functions, which is to suppress the expression of other genes.

Although previous studies had found that the TBX2 gene played essential roles in mouse development, and chromosomal deletions and duplications involving the human TBX2 gene have been associated with human cardiac and skeletal defects, a direct link between pathogenic mutations in TBX2 and a Mendelian syndrome has not been described before.

"A living test tube"

"Determining the functional consequences of missense mutations such as these ones - mutations that change a single amino acid in a protein - is still very difficult, even with the help of various bioinformatics tools," said Yamamoto.

Here is where the fruit fly came in. To further evaluate the biological significance of TBX2 mutations on complex signaling pathways in an intact animal, the researchers designed and conducted several assays in fruit flies in the laboratories of Dr. Yamamoto, Dr. Michael Wangler and Dr. Hugo Bellen, who oversee the UDN's Model Organism Screening Center, located in Baylor.

"We used fruit flies as 'living test tubes' in which we tested the effects of variations of the TBX2 gene on various biological processes and pathways," Yamamoto said.

Typically, researchers explore the genetic bases of disease in mouse or other animal models by introducing in the models gene mutations that mimic key characteristics of the human condition under study. There are occasions, however, in which human diseases are hard to mimic in animal models, but in those cases the laboratory fruit fly offers the opportunity to quickly provide functional information on rare and potentially disease-causing mutations. The researchers approached the TBX2 gene puzzle by working both with cells in the laboratory and with fruit flies, conducting morphological and functional assays that do not seem to be related to the patients' conditions. These studies uncovered a link between the congenital heart defects, skeletal abnormalities, immune and endocrine defects in patients and the partial loss-of-function of protein TBX2.

"The human and fly circulatory and immune systems are structurally different, and flies do not have an endoskeleton system. Therefore, in this study, instead of using fruit flies to model the symptoms found in patients, we used flies as a rapid diagnostic tool to test whether the functional differences in TBX2 we found in cells in the laboratory had biological significance in a live animal," said Yamamoto. "The fruit fly's equivalent to the human TBX2 gene, called bifid, is important for the proper development of the fly, especially for the visual and nervous systems. We used the development and retinal function of adult fruit fly eyes as a readout for the activity of TBX2 gene."

Consistent with the results from experiments in cells, the experiments with fruit flies revealed that the TBX2 genetic variants in patients moderately affected the flies' eye development, retinal function and lifespan, all of which unequivocally point to the pathogenic potential of these variants.

"This study provides a blueprint of how fruit flies can be used as a rapid screening tool to identify potentially pathogenic human genes," Yamamoto said.

Writing in the journal eLife, the team reveals that this disease is caused by a recessive mutation in CAMK2A - a gene that is well known for its role in regulating learning and memory in animals. The findings suggest that dysfunctional CAMK2 genes may contribute to other neurological disorders, such as epilepsy and autism, opening up potential new avenues for treating these conditions.

"A significant number of children are born with growth delays, neurological defects and intellectual disabilities every year across the world," explains senior author Bruno Reversade, Research Director at the Institute of Medical Biology and Institute of Molecular and Cell Biology, A*STAR, Singapore, who supervised the study. "While specific genetic mutations have been identified for some patients, the cause remains unknown in many cases. Identifying novel mutations would not only advance our understanding of neurological diseases in general, but would also help clinicians diagnose children with similar symptoms and/or carry out genetic testing for expecting parents."

The team's research began when they identified a pair of siblings who demonstrated neurodevelopmental delay with frequent, unexplained seizures and convulsions. While the structure of their bodies developed normally, they did not gain the ability to walk or speak. "We believed that the children had novel mutations in CAMK2A, and we wanted to see if this were true," says Reversade.

The fully functional CAMK2A protein consists of multiple subunits. Using a genomic technique called exome sequencing, the team discovered a single coding error affecting a key residue in the CAMK2A gene that prevents its subunits from assembling correctly.

Moving their studies into the roundworm Caenorhabditis elegans, the scientists saw that this mutation disrupts the ability of CAMK2A to ensure proper neuronal communication and normal motor function. This suggests that the mutation is indeed the cause of the neurodevelopmental defects seen in the siblings.

To the best of the team's knowledge, this new disorder represents the first human disease caused by inherited mutations on both copies of the CAMK2A gene. In addition, another report published recently identified single-copy mutations on both CAMK2A and CAMK2B that caused intellectual disabilities as soon as the mutations occurred. "We would like to bring these findings to the attention of those working in the area of paediatric genetics, such as clinicians and genetic counsellors, as there are likely more undiagnosed children with similar symptoms who have mutations in their CAMK2A gene," explains co-first author Franklin Zhong, Research Scientist in Reversade's lab at A*STAR.

"Neuroscientists working to understand childhood brain development, neuronal function and memory formation also need to consider this new disease, since CAMK2A is associated with these processes. In future, it would be interesting to test whether restoring CAMK2A activity can bring therapeutic benefit to patients with this condition, as well as those with related neurological disorders."

London, UK (Scicasts) — A major new analysis reveals for the first time the likely cause of most cases of childhood leukaemia, following more than a century of controversy about its origins.

Professor Mel Greaves from The Institute of Cancer Research, London, assessed the most comprehensive body of evidence ever collected on acute lymphoblastic leukaemia (ALL) - the most common type of childhood cancer.

His research concludes that the disease is caused through a two-step process of genetic mutation and exposure to infection that means it may be preventable with treatments to stimulate or 'prime' the immune system in infancy.

The first step involves a genetic mutation that occurs before birth in the foetus and predisposes children to leukaemia—but only 1 per cent of children born with this genetic change go on to develop the disease.

The second step is also crucial. The disease is triggered later, in childhood, by exposure to one or more common infections, but primarily in children who experienced 'clean' childhoods in the first year of life, without much interaction with other infants or older children.

Acute lymphoblastic leukaemia is particularly prevalent in advanced, affluent societies and is increasing in incidence at around 1 per cent per year.

Professor Greaves suggests childhood ALL is a paradox of progress in modern societies—with lack of microbial exposure early in life resulting in immune system malfunction.

In a landmark paper published in Nature Reviews Cancer today, Professor Greaves compiled more than 30 years of research—his own and from colleagues around the world—into the genetics, cell biology, immunology, epidemiology and animal modelling of childhood leukaemia. The research in his lab at The Institute of Cancer Research (ICR) was largely funded by the charities Bloodwise and The Kay Kendall Leukaemia Fund.

Instead, he presented strong evidence for a 'delayed infection' theory for the cause of ALL, in which early infection is beneficial to prime the immune system, but later infection in the absence of earlier priming can trigger leukaemia.

Professor Greaves suggests that childhood leukaemia, in common with type I diabetes, other autoimmune diseases and allergies, might be preventable if a child's immune system is properly 'primed' in the first year of life—potentially sparing children the trauma and life-long consequences of chemotherapy.

His studies of identical twins with ALL showed that two 'hits' or mutations were required. The first arises in one twin in the womb but produces a population of pre-malignant cells that spread to the other twin via their shared blood supply. The second mutation arises after birth and is different in the two twins.

Population studies in people together with animal experiments suggest this second genetic 'hit' can be triggered by infection—probably by a range of common viruses and bacteria. In one unique cluster of cases investigated by Professor Greaves and colleagues in Milan, all cases were infected with flu virus.

Researchers also engineered mice with an active leukaemia-initiating gene, and found that when they moved them from an ultra-clean, germ-free environment to one that had common microbes, the mice developed ALL.

Population studies have found that early exposure to infection in infancy such as day care attendance and breast feeding can protect against ALL, most probably by priming the immune system. This suggests that childhood ALL may be preventable.

Professor Greaves is now investigating whether earlier exposure to harmless 'bugs' could prevent leukaemia in mice—with the possibility that it could be prevented in children through measures to expose them to common but benign microbes.

Professor Greaves emphasises two caveats. Firstly, while patterns of exposure to common infections appear to be critical, the risk of childhood leukaemia, like that of most common cancers, is also influenced by inherited genetic susceptibility and chance. Secondly, infection as a cause applies to ALL specifically—other rarer types including infant leukaemia and acute myeloid leukaemia probably have different causal mechanisms.

Professor Mel Greaves, Director of the Centre for Evolution and Cancer at The Institute of Cancer Research, London, said:

"I have spent more than 40 years researching childhood leukaemia, and over that time there has been huge progress in our understanding of its biology and its treatment—so that today around 90 per cent of cases are cured. But it has always struck me that something big was missing, a gap in our knowledge—why or how otherwise healthy children develop leukaemia and whether this cancer is preventable.

"This body of research is a culmination of decades of work, and at last provides a credible explanation for how the major type of childhood leukaemia develops. The research strongly suggests that ALL has a clear biological cause, and is triggered by a variety of infections in predisposed children whose immune systems have not been properly primed. It also busts some persistent myths about the causes of leukaemia, such as the damaging but unsubstantiated claims that the disease is commonly caused by exposure to electro-magnetic waves or pollution.

"I hope this research will have a real impact on the lives of children. The most important implication is that most cases of childhood leukaemia are likely to be preventable. It might be done in the same way that is currently under consideration for autoimmune disease or allergies—perhaps with simple and safe interventions to expose infants to a variety of common and harmless 'bugs'." Professor Paul Workman, Chief Executive of The Institute of Cancer Research, London, said:

"This research has been something of a personal, 30-year quest for Professor Mel Greaves—who is one of the UK's most influential and iconic cancer researchers. His work has cut through the myths about childhood leukaemia and for the first time set out a single unified theory for how most cases are caused.

"It's exciting to think that, in future, childhood leukaemia could become a preventable disease as a result of this work. Preventing childhood leukaemia would have a huge impact on the lives of children and their families in the UK and across the globe."

Evanston, IL (Scicasts) — Though mutations in a gene called MLL3 are common across many types of cancers, their relationship to the development of the disease has been unclear.

Now, study has identified an epigenetic imbalance that silences the expression of tumour-suppressing proteins, allowing cancerous cells to proliferate.

In the study published in Nature Medicine, Northwestern investigators applied a simple molecular inhibitor that reversed epigenetic imbalance in laboratory models. This inhibitor has a potential therapeutic application, and the study will be followed by a clinical trial led by Northwestern investigators.

"This is a simple molecular concept with major clinical significance," said Dr. Ali Shilatifard, director of the Simpson Querrey Center for Epigenetics, chair of Biochemistry and Molecular Genetics, Robert Francis Furchgott Professor and senior author of the study.

Mutations in MLL3, a component of a complex named COMPASS discovered by Shilatifard's laboratory, were one of the most frequently identified mutations in cancer, according to an analysis of publically available genomic data performed as part of the current study.

"Among all of the histone modifiers and transcription factors we analyzed, we found this protein was on top of the list with two significant hot-spot mutations," said Dr. Lu Wang, a postdoctoral research fellow in the Shilatifard laboratory and lead author on the study. "We found it was present in 7 percent of primary tumours — and in metastatic tumours, the rate of mutation was even higher."

The investigators found the presence of MLL3 hot-spot mutations was correlated with significantly lower cancer survival rates, indicating there was some oncogenic mechanism triggered by the mutations. After a series of biochemical experiments, they found success when examining the relationship between MLL3 and a molecule complex called PRC2.

MLL3, as part of COMPASS, normally promotes the expression of numerous tumour-suppressing genes that are immediately downstream. However, the study found that if there are specific mutations in MLL3, it will not be recruited to the right location on the genome. Instead, PRC2 becomes dominant and prevents downstream tumor-suppressor gene expression.

"If you silence the tumour suppressors, you get an increased risk of tumours," Wang said.

Having identified the mechanism that leads to cancerous growth, the investigators' next effort was to interrupt the cycle. By applying a small PRC2 inhibitor, preventing PRC2 from silencing the downstream tumour-suppressor genes, the scientists were able to restore normal function and slow tumour growth.

"The balance in this mechanism was restored," Wang said. "In our models, these downstream tumour suppressors were turned on again and the tumours started to shrink in our xenograft model."

According to the authors, this pathway has therapeutic potential; Northwestern Medicine investigators have begun laying the groundwork for a clinical study. Dr. Josh Meeks, assistant professor of Urology and co-author of the Nature Medicine study, will be leading a clinical trial of the method along with Dr. Maha Hussain, the Genevieve E. Teuton Professor of Medicine and deputy director of the Robert H. Lurie Comprehensive Cancer Center of Northwestern University.

The trial will treat patients with both advanced-stage bladder cancer and the MLL3 mutations with the PRC2 inhibitor, investigating if the inhibitor can improve survival rates. If it works, the implications could be significant, according to Shilatifard.

"MLL3 mutations are found in a large number of tumours," Shilatifard said. "If this works in the clinic — which our pre-clinical data suggests it will — it could have a vast application to other human cancers caused by MLL/COMPASS mutations as well."

Meeks is also an assistant professor of Biochemistry and Molecular Genetics, Hussain is also a professor of Medicine in the Division of Hematology and Oncology and Shilatifard is also a professor of Pediatrics.

Epigenetic Regulation Through Transcription

The central concept behind the Nature Medicine study — epigenetic errors leading to cancer — was first identified by Shilatifard's laboratory over 20 years ago. That discovery opened up a new area of inquiry, according to a new review published in Nature Reviews Molecular Cell Biology.

"RNA polymerase II transcribes genes, but something happens with certain mutations that make it go faster," said Shilatifard, who was senior author of the review. "The rate of elongation is increased upon mutations in cancer — we showed this 20 years ago in Science, and it has proven to be correct for a large number of cancers."

Correcting imbalance in transcription, as shown in the Nature Medicine study, could be put to use in other cancers as well, according to Shilatifard.

"We think this is a central dogma for future therapy," Shilatifard said.